Ocular oscillations induced by shifts of the direction and depth of visualfixation

Shifts of the point of fixation between two targets aligned on one eye that are located near and far (Muller paradigm) stimulates a combined saccadic- vergence movement. In normal subjects, this test paradigm often induces sac cadic oscillations of about 0.3 degrees at 20 to 30 Hz. We measured eye mov ements using the magnetic search coil technique in 2 patients recovering fr om viral opsoclonus-myoclonus syndrome, comparing saccadic-vergence respons es to the Muller paradigm with conjugate saccades between distant targets. Both patients exhibited intermittent conjugate ocular oscillations of about 4 to 5 degrees amplitude at about 10 Hz. Combined saccadic-vergence moveme nts induced these oscillations twice as often as did conjugate saccades. On e patient also exhibited disjunctive ocular oscillations at 10 Hz while sus taining fixation on the near target. The Muller paradigm provides a useful clinical and experimental technique for inducing saccadic oscillations. The probable mechanism is that pontine omnipause neurons, which normally gate saccades, are inhibited during the sustained vergence movement that follows the saccadic component of the response to the Muller paradigm.